1. Field of the Invention
The present invention relates to an arrangement structure of a speed-change cable. More specifically, to an arrangement structure of a speed-change cable in a transmission for a bicycle.
2. Description of Background Art
A connecting portion of the speed-change cable connected to a derailleur in the transmission for a bicycle in the related art is located at the rear portion of the bicycle because the position to arrange the derailleur is in the vicinity of an axle of a rear wheel. Thus, the speed-change cable to be connected to the derailleur is arranged so as to extend from the connecting portion towards the rear of the vehicle body, inverted to form a curved portion, and extend to a speed-change operation member on a handle at the front of the vehicle body. See, for example, JP-A-8-219139 pages 3-4 and FIG. 4-FIG. 5.
As shown in FIGS. 20(a) and 20(b), the derailleur operating cable in the transmission for a bicycle disclosed in JP-A-8-219139 is configured in such a manner that a connecting portion at one end of an operating wire 02, which is an inner cable of the cable 01 is connected to the derailleur, not shown in FIGS. 20(a) and 20(b). Thus, the operating wire 02, which is the inner cable of the cable 01, is pulled or slackened to operate the derailleur by speed-change operation of a speed-change operating element provided on the handle, not shown, to select a desired speed gear.
Among others, the rear derailleur operating cable 01 is arranged so as to have an extending portion 03 from the connecting portion to the rear derailleur, not shown, rearwardly of the vehicle body, inverted to form a curved portion 04, extending along a lower horizontal frame 05 or a obliquely upwardly extending frame 06 of the vehicle body. The cable 01 further extends along the oblique frame 07 or a horizontal frame 08 and extends towards the speed-change operating element, not shown, provided on the handle at the front of the vehicle body, and connected to the speed-change operating element at the extended end, which is the other end of the cable 01, via the wire 02, which is the inner cable.
The above-described derailleur operating cable 01 which extends at portion 03 from the connecting portion to the rear derailleur rearwardly of the vehicle body and then is inverted and extends towards the front of the vehicle body cannot avoid the existence of the curved portion 04 in the course of the extension thereof. The existence of the curved portion 04 causes a frictional force between the operating wire 02, which is the inner cable of the cable 01, and the outer cable at the curved portion. Consequently, an operating load in operating the derailleur increases, and the smooth operability thereof is impaired. Thus, increases in the length of the operating cable 01 due to the existence of the curved portion 04 cannot be avoided.
Because of the arrangement structure of the above-described operating cable, the existence of the curved portion cannot be avoided in the extension forwardly of the vehicle body. Thus, a reduction of the operating load for the speed-change is difficult due to its structure, and the securement of good operability is limited. There is also a problem that a reduction in the length of the operating cable cannot be achieved.